Hampton Beach Casino Ballroom Chow
I'm not sure how casual you're looking for, but I like Ron's Landing and The Beach House, both on Ocean Blvd up from the strip, in Hampton (upscale/casual). I've eaten at each at least 10-15 times and have never been disappointed. Prices are all ranges with higher entrees around $25 but you can make a meal out of appetizers. A couple of my favorites at Ron's is the veal pistachio - veal with pistachio nut crust and stuffed with lobster, and the wild mushroom ragout over pasta - although I usually just order appetizers. The Beach House always has great specials. Both places have cozy, casual bar areas to sit and grab some appetizers and/or seafood, which I usually prefer.
Info on Beach House:
Info for Ron's at (Link below).
Also, for Chinese, I like Ocean Wok at 70 Ocean Blvd.
One place to avoid - Little Jack's Seafood Restaurant on 539 Ocean Blvd. (probably closed for the winter). I thought it was terrible - seafood not fresh, and overcooked.
Please heed Rubee's warning about Little Jack's. My entire family got sick from eating there a few years back. We called after the fact and complained and management was not helpful at all essentially telling us that you take that risk when you eat seafood. Sorry Jack, we'll risk it somewhere else from now on.
As for the rest of Hampton, one word - CHEESY. It can be an interesting day though. The people watching is entertainment in itself. I do love Blink's Fried Dough though. I have to go at least once a summer just because eating that fried dough on the beach puts me in the spirit of summer.
Ditto on Little Jack's. You have been warned thrice. If you decide to stay in the area overnight you might consider driving to Portsmouth for dinner. Many excellent choices there - search the New England board for recommendations (my personal favorite is the Blue Mermaid).
For spots local to the beach area Ron's Landing and the Beach House are probably your best bets. Both are open now. Most places at Hampton Beach are boarded up now.
If you go into Hampton proper the Old Salt has reopened at Lamey's Inn - located at the corner of Rt 27 and Rt 1. The Old Salt was a landmark down on the beach that burned down a couple of years ago, the owners decided to reopen in town instead of shelling out the $Ms it was going to take to rebuild at the beach. If you fried seafood, lobster, clams etc.. I'd go to the Old Salt. Also in town is the Galley Hatch, Old Salt is better IMHO. There is also a place called Atlantic Grill that is on Rt. 27 (High Street) about a 1/2 block from Rt.1, towards the beach. Atlantic Grill is a "surfer" hangout, they have a very limited menu and are only open on Wed-Sat. Of all the places in Hampton and Hampton Beach, Ron's Landing is the most sophisticated.
Regarding Little Jack's. The owner died about 2 years ago and the family sold the business. It never opened last summer. The business was sold and will reopen under the same name this summer. Hopefully the new owners will clean it up.
If you have the time/desire I'd go to Portsmouth and eat at Jumpin Jay's Fish House. You MUST have reservations for any day of the week. The only way to get served if you walk in is to sit/eat at the bar. Seats at the bar are on a waiting list.
Lots of places in Hampton Beach itself are closed in the off-season, it's a very "honky-tonk" (as the above poster mentioned) summer touristy kind of place (think lots of fried dough and salt water taffy). Even in summer, good chowhoundy choices are pretty slim. However, the town of Hampton itself is nice, and the next town up the beach, Rye, is beautiful. I would do a search for b&bs in Rye or the town of Hampton on google.com. One nice hotel in the middle of Hampton Beach that might be open year round is the Ashford, they have a website. They also have a restaurant. BTW, skip Salisbury,the next town down the beach. It's kind of grungy (rough bars and strip club). Have fun!